中部天山林线动态对气候变化的响应研究

中部天山高山林线构成一个对气候变化及其变化程度的理想而敏感的代表性指标，低温、干旱和水分胁迫等都可能限制森林的分布和影响林线的形成。本文通过沿海拔梯度定位调查高山林线样地天山云杉种群的更新情况，利用树木年轮气候学和生态学方法，研究了林线天山云杉种群的时间动态和空间动态及其与气候变化的关系，并取得了一些初步结果。 利用不同年龄的树木年轮序列建立了三个不同年龄的树木年轮宽度年表，幼龄(<100年)，中龄(100-200年)和老龄(>200年) 树木都与当年生长季前期1-3月份的温度显著正相关，和当年1月份和7月份的降水显著正相关。但不同年龄的天山云杉对气候变化的响应结果不同，幼龄(<100年)天山云杉对气候变化的响应程度随年龄的增加而增加，但变化趋势不明显；中龄树木(100-200年)对气候变化的响应随年龄的增加而降低；老龄(>200年)天山云杉受年龄的影响不大。 有关古气候变化的相关研究中，都是尽可能采取年代长的树木年轮样本建立年代较长的年表，并利用最近几十年的气候资料与最近几十年的树木生长的相关关系来重建古气候变化情况。本文的研究结果表明，将不同年龄天山云杉的树木年轮宽度序列放在一起所建成的多年龄复合年表包含有更多的气候信息，显示出当地天山云杉种群对气候变化反应的共性。研究结果表明在建树木年轮的宽度年表时，选用一定数量的不同年龄的树木年轮宽度序列可增强年表对气候变化的响应关系。 利用不同年龄的天山云杉样本建成的复合年龄的树木年轮宽度年表对冬季的最低温度的响应关系，重建了中部天山高山林线地区过去300年来的冬季最低温度。重建的冬季最低温度的有几个明显的暖期和冷期，20世纪50年代以来冬季低温则表现出显著增高的变化趋势。 中部天山高山林线天山云杉种群的胸径和年龄结构以都呈倒-J型分布，说明天山云杉种群更新良好，处于稳定发展时期。随着全球变暖和温度的升高，20世纪以来中部天山高山林线天山云杉的种群更新数量较多，天山云杉的密度有所增加，但林线位置并没有显著的上升，不同年代内更新的树木所到达的海拔高度也不一样。中部天山高山林线天山云杉种群发生的时间动态主要和冬季最低温度正相关，而不同时间内更新的天山云杉种群空间动态形成原因比较复杂，主要和冬季低温负相关。

Exploratory temperature and precipitation reconstructions from the Qinling Mountains, north-central China

IEECAS SKLLQG

Vegetation and climate variations at Taibai, Qinling Mountains in central China for the last 3 500 cal BP

IEECAS SKLLQG

Status and distribution pattern of black crested gibbon (Nomaseas concolor jingdongensis) in Wuliang Mountains, Yunnan, China: implication for conservation

The western black crested gibbon (Nomascus concolor), or black gibbon, one of the lesser apes (Hylobatidae), is mainly distributed in Yunnan, China. Of the four recognized subspecies, N. c. jingdongensis is endemic to the Wuliang Mountain, central Yunnan,

Gibbons under seasonal stress: the diet of the black crested gibbon (Nomascus concolor) on Mt. Wuliang, Central Yunnan, China

The diet of a habituated group of black crested gibbon (Nomascus concolor jingdongensis) was studied from March 2005 to April 2006 in the Wuliang Mountains, central Yunnan, China. Gibbons consumed 77 different plant species, one mammal-, two bird-, one li

Microgravity Smoldering Combustion Of Flexible Polyurethane Foam With Central Ignition

Smoldering constitutes a significant fire risk both in normal gravity and in microgravity. This space experiment has been conducted aboard the China Recoverable Satellite SJ-8 to investigate smoldering characteristics of flexible polyurethane foam with central ignition in a forced flow of oxidizer. This configuration resulted in a combination of opposed and forward flow smolder. The microgravity experiment is rather unique in that it was performed at constant pressure, and with a relatively high ambient oxygen concentration (35% by volume). The smoldering characteristics are inferred from measurements of temperature histories at several locations along the foam sample. Particularly important is the discovery that there is a transition from smoldering to flaming near the sample end in the opposed smoldering. This transition seems to be caused by strong acceleration of the smoldering reaction. The observed transition serves to initiate a vigorous forward-propagating oxidation reaction in the char left behind by the smoldering reaction. The secondary char oxidation reaction propagates through the sample and consumes most of the remaining char. In forward flow smoldering, the oxidizer depletion by the upstream opposed smolder prevents an exothermic oxidation reaction from being established in the foam until this preceding reaction is completed. Once fresh oxidizer flows in the sample, the existing conditions are sufficient for a self-sustained forward smoldering reaction to take place.